ios-UI高级 GCD队列组合成图片

#import "ViewController.h"

@interface ViewController ()

//这个imageView是storyBoard里面的

@property (weak, nonatomic) IBOutletUIImageView *GruopImageView; 

//这两个是自定义的Image

@property (nonatomic,strong)UIImage *image1;

@property (nonatomic,strong)UIImage *image2;

@end

@implementation ViewController

- (void)viewDidLoad {

    [superviewDidLoad];

    

}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{

    dispatch_queue_t queue =dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0);

    dispatch_group_t group =dispatch_group_create();

    

    dispatch_group_async(group, queue, ^{

        //获得image1的图片地址

        NSURL *image1Url = [NSURLURLWithString:@"http://f.hiphotos.baidu.com/image/pic/item/3812b31bb051f8196bc52fa8dfb44aed2f73e774.jpg"];

        //加载image1

        NSData *data1 = [NSDatadataWithContentsOfURL:image1Url];

        self.image1= [UIImageimageWithData:data1];

    });

    dispatch_group_async(group, queue, ^{

        //获得image2的图片地址

        NSURL *image2Url = [NSURLURLWithString:@"http://photocdn.sohu.com/20151124/mp43786429_1448294862260_4.jpeg"];

        //加载image2

        NSData *data2 = [NSDatadataWithContentsOfURL:image2Url];

        self.image2= [UIImageimageWithData:data2];

    });

    //合成image1和image2(notify的作用是当它前面的都执行完才执行它）

    dispatch_group_notify(group, queue, ^{

        //开启上下文

        UIGraphicsBeginImageContext(CGSizeMake(200, 200));

        

        [self.image1drawInRect:CGRectMake(0, 0, 100, 200)];

        [self.image2drawInRect:CGRectMake(100, 0, 100, 200)];

        

        //获得上下文

        UIImage *image =UIGraphicsGetImageFromCurrentImageContext();

        

        //结束上下文

        UIGraphicsEndImageContext();

        //回到主队列

        dispatch_async(dispatch_get_main_queue(), ^{

            self.GruopImageView.image = image;

        });

        

    });

}

- (void)didReceiveMemoryWarning {

    [superdidReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

@end

运行效果：